Table of contents for Steve Farrar's book, How to Ruin Your Life by Age 30...
•Ignore the law of cause & effect (choices have consequences)
•Refuse to take responsibility for your actions (victim-mentality)
•Neglect your gifts & strengths
•Disregard what the Bible says about sex & marriage
Pretty sound advice, and the rest is likely worth reading; he also has one for age 40.